Conventionally, as methods of measuring subcutaneous fat thickness, the following are known: a method using ultrasonic waves (see, for example, Japanese Patent No. 2953909) ; a method using near infrared rays (see, for example, Japanese Patent No. 3035791); and a method using a caliper (see, for example, Japanese Laid-Open Patent Application No. H10-314145). Moreover, it has been reported that the visceral fat area is highly correlated with a waist girth (see, for example, Yuji MATSUZAWA and 13 others, “Atarashii himan no hantei to himansho no shindan kijun (new obesity determination and obesity diagnosis criteria), Himan Kenkyu (obesity research), Vol. 6, No. 1, 2000 <Committee Report> Obesity Diagnosis Criteria Examination Committee of the Japan Society for the Study of Obesity).
The disclosure of Japanese Patent No. 2953909, Japanese Patent No. 3035791, and “Yuji MATSUZAWA and 13 others, “Atarashii himan no hantei to himansho no shindan kijun (new obesity determination and obesity diagnosis criteria), Himan Kenkyu (obesity research), Vol. 6, No. 1, 2000 <Committee Report> Obesity Diagnosis Criteria Examination Committee of the Japan Society for the Study of Obesity” are incorporated herein by reference in their entireties.
However, according to a conventional method using ultrasonic waves or near infrared rays, since measurement is performed by bringing ultrasonic waves or near infrared rays into contact with a measurement part, subcutaneous fat which is soft becomes deformed. Variations in the condition of a contact with a measurement part make the measured subcutaneous fat thickness unstable, thereby degrading measurement repeatability. In addition, since the subcutaneous fat becomes deformed, the obtained subcutaneous fat thickness is different from the value in the natural state in which no force is applied to the measurement part. On the other hand, according to the method using a caliper, it is difficult to accurately determine the measurement place. In addition, since the manner in which a skin is pulled and the measurement method vary among measurers, the measurement value varies.
With respect to a waist girth which has been reported to be highly correlated with a visceral fat area, since the ratio between subcutaneous fat and visceral fat differs among persons (in particular, between men and women), there is no difference in waist girth between persons who are thick in subcutaneous fat and small in the amount of visceral fat and persons who are thin in subcutaneous fat and large in the amount of visceral fat although there is a difference in visceral fat area. That is, a waist girth is an information amount not considering the influence of subcutaneous fat although correlated with a visceral fat amount. Moreover, when a tape measure is used to measure a waist girth, the measurement repeatability of the waist girth is inferior because the strength of pulling of the tape measure varies among measurers.